The present invention is directed to a rehydration capsule or a system for hydrating media, such as cell culture media which is typically used to grow cells such as mammalian cells and bacteria, as for example, the GIPCO® AGT media, using a capsule filled with such media and circulating water in the capsule until the media is dissolved. Typically, such media are rehydrated by using mechanical mixers. Such mixers, however, require significant operator skill in ensuring that the media is properly introduced to the mixer in the correct amount and, more importantly, without contamination. Conventional mixers are typically constructed of stainless steel and must be thoroughly cleaned after each use. This cleaning process is time consuming and difficult. The cleaning method and procedure must also be carefully validated to be consistent and sufficiently clean. This validation step is challenging and difficult. To overcome the problems related to cleaning, single use mixers are now widely available. Single use mixers are designed so that all wetted components are used only once and are discarded after each use and typically consist of an appropriately sized multi-layer plastic chamber with integrated agitator which is often magnetically coupled so that the plastic chamber is completely closed and isolated from the drive system. However, such mixers are expensive. Thus, it is desirable to have a system that can contain the proper amount of media to be hydrated and which can be easily installed by an operator without concern for contamination or errors. The meaning of “hydrated media” as used herein means that the media is completely dissolved in the hydrating liquid, whereby the media is no longer a solid.